Process to prepare paraffin wax

ABSTRACT

The present invention provides a paraffin wax having a congealing point according to ASTM D938 of at least 75° C. and a Saybolt colour according to ASTM D156 of at least 25 cm.

The present invention provides a paraffin wax and a process to preparesaid paraffin wax.

Paraffin wax may be obtained by various processes. U.S. Pat. No.2,692,835 discloses a method for deriving paraffin wax from crude oil.Also, paraffin wax may be obtained using the so called Fischer-Tropschprocess. An example of such process is disclosed in WO 2002/102941, EP 1498 469, WO 2004/009739 and WO 2013/064539.

WO 2000/11113 discloses a process to prepare Fischer-Tropsch derived waxproducts, by feeding a Fischer-Tropsch derived paraffinic into adistillation column, followed by operating the distillation column toproduce wax products, which wax products are withdrawn from thedistillation column.

A problem of the process disclosed in WO 2000/11113 is that althoughthis process delivers wax products, the wax products are not refinedenough to be used in applications such as candles, hot melt adhesives,crayons, packaging, and PVC extrusion lubricants in an advantageous way.

It is an object of the invention to solve or minimize at least of one ofthe above problems. It is a further object of the present invention toprovide a paraffin wax which can be advantageously used in applicationssuch as candles, hot melt adhesives, crayons, packaging, and PVCextrusion lubricants.

Moreover, an object of the present invention is to provide an efficientmethod for preparing refined paraffin wax product in a high yield. Oneof the above or other objects may be achieved according to the presentinvention by providing a paraffin wax having a congealing pointaccording to ASTM D938 of at least 75° C. and a Saybolt colour accordingto ASTM D156 of at least 25 cm.

It has now surprisingly been found according to the present inventionthat the paraffin wax is a fully refined wax which may be advantageouslyused in several wax applications.

An important advantage of the present invention is that the paraffin waxmay be advantageously used in wax applications such as candles, hot meltadhesives, crayons, packaging, and PVC extrusion lubricants.

In another embodiment of the present invention there is provided aprocess to prepare Fischer-Tropsch paraffin waxes.

An advantage of said process according to the present invention is thatby distilling the Fischer-Tropsch derived feed without a precedinghydrogenation step results in paraffin waxes having high Sayboltcolours.

The relation between hydrogenation of the Fischer-Tropsch derived feedand the Saybolt colour of Fischer-Tropsch derived waxes is for exampledescribed on page 181 in the “Handbook of Commercial Catalysts,Heterogeneous catalysts”, Howard F. Rase, CRC Press LLC, Florida, 2000,ISBN 0-8493-9417-1.

A further advantage is that the hydrogenated Fischer-Tropsch productstream is more stable with respect to product degradation in subsequentdistillation steps. Degradation may be caused by exposure to hightemperature and by oxygen ingress in vacuum columns. Hydrogenationgenerally results in higher quality of the normal paraffinic products,e.g. in terms of colour or odour.

The following detailed description does not limit the invention.Instead, the scope of the invention is defined by the appended claims.

According to the present invention, a paraffin wax has a congealingpoint according to ASTM D938 of at least 75° C.

The paraffin wax comprises primarily n-paraffins. The paraffin waxaccording to the present invention comprises more than 85 wt. % ofn-paraffins, preferably more than 90 wt. % of n-paraffins.

Paraffin waxes are known and described for example in U.S. Pat. No.2,692,835, WO2002/102941, EP 1 498 469 and WO 2004/009739.

Suitably, the paraffin wax according to the present invention has acongealing point according to ASTM D938 in the range of from 75 to 85°C.

Also, the paraffin wax according to the present invention has acongealing point according to ASTM D938 of at least 80° C.

Further, the paraffin wax according to the present invention has aSaybolt colour according to ASTM D156 of at least 25 cm.

Preferably, the paraffin wax according to the present invention has aSaybolt colour according to ASTM D156 of at least 30 cm.

Typically, the Saybolt colour scale is used to quantify colour intensityfor mildly coloured substances in liquid state. For this objective waxesare molten for measurement. The scale runs from <−16 cm to >30 cm. >30cm means water white. The higher the number the better (i.e. the lesser)the colour.

The paraffin wax according to the present invention has preferably anoil content according to ASTM D721 of less than 0.5 wt. %, morepreferably less than 0.45 wt. %.

It is preferred that the paraffin wax according to the present inventionis a Fischer-Tropsch derived paraffin wax.

The Fischer-Tropsch derived paraffin wax is derived from aFischer-Tropsch process. Fischer-Tropsch product stream is known in theart. By the term “Fischer-Tropsch derived” is meant a paraffin wax is,or is derived from a Fischer-Tropsch process. A Fischer-Tropsch derivedparaffin wax may also be referred to a GTL (Gas-to-Liquids) product. Anexample of a Fischer-Tropsch process is given in WO2002/102941, EP 1 498469 and WO2004/009739, the teaching of which is incorporated byreference.

The Fischer-Tropsch derived paraffin wax comprises paraffins, primarilyn-paraffins. Preferably, the Fischer-Tropsch derived paraffin waxcomprises more than 85 wt. % of n-paraffins, preferably more than 90 wt.% of n-paraffins.

In a further aspect, the present invention provides a process to preparea Fischer-Tropsch derived paraffin wax, the process at least comprisingthe following steps:

(a) providing a Fischer-Tropsch product stream comprising paraffinshaving from 10 to 300 carbon atoms;(b) separating the Fischer-Tropsch product stream of step (a), therebyobtaining at least a fraction comprising 10 to 17 carbon atoms and afraction comprising 18 to 300 carbon atoms;(c) subjecting the fraction comprising 18 to 300 carbon atoms of step(b) to a hydrogenation step, thereby obtaining a hydrogenated fractioncomprising 18 to 300 carbon atoms;(d) separating the hydrogenated fraction comprising 18 to 300 carbonatoms of step (c), thereby obtaining one or more first light waxeshaving a congealing point in the range of 30 to 75° C. and a secondheavy wax having a congealing point in the range of 75 to 120° C.;(e) separating the heavy wax of step (d) to obtain a distillate waxfraction having a congealing point of at least 75° C., preferably of atleast 80° C.;f) hydrofinishing the distillate wax fraction of step (e) therebyobtaining a hydrofinished distillate wax fraction having a congealingpoint of at least 75° C., preferably of at least 80° C.

In step (a) of the process according to the present invention aFischer-Tropsch product stream comprising paraffins having from 10 to300 carbon atoms is provided.

By the part “a Fischer-Tropsch product stream comprising paraffinshaving from 10 to 300 carbon atoms is meant 10 to 300 carbon atoms permolecule.

The Fischer-Tropsch product stream as provided in step (a) is derivedfrom a Fischer-Tropsch process. Fischer-Tropsch product stream is knownin the art. By the term “Fischer-Tropsch product” is meant a synthesisproduct of a Fischer-Tropsch process. In a Fischer-Tropsch processsynthesis gas is converted to a synthesis product. Synthesis gas orsyngas is a mixture of hydrogen and carbon monoxide that is obtained byconversion of a hydrocarbonaceous feedstock. Suitable feedstock includenatural gas, crude oil, heavy oil fractions, coal, biomass and lignite.A Fischer-Tropsch product derived from a hydrocarbonaceaous feedstockwhich is normally in the gas phase may also be referred to a GTL(Gas-to-Liquids) product. The preparation of a Fischer-Tropsch producthas been described in e.g. WO2003/070857.

The product stream of the Fischer-Tropsch process is usually separatedinto a water stream, a gaseous stream comprising unconverted synthesisgas, carbon dioxide, inert gasses and C1 to C3, and a C4+ stream.

The full Fischer-Tropsch hydrocarbonaceous product suitably comprises aC1 to C300 fraction.

Lighter fractions of the Fischer-Tropsch product, which suitablycomprises C3 to C9 fraction are separated from the Fischer-Tropschproduct by distillation thereby obtaining a Fischer-Tropsch productstream, which suitably comprises C10 to C300 fraction.

The weight ratio of compounds having at least 60 or more carbon atomsand compounds having at least 30 carbon atoms in the Fischer-Tropschproduct is preferably at least 0.2, more preferably 0.3.

Suitably, in case of preparation of Fischer-Tropsch derived wax fractionhaving a congealing point of above 90° C. weight ratio is at least 0.5.The weight ratio in the Fischer-Tropsch product may lead toFischer-Tropsch derived paraffin waxes having a low oil content.

In step (b) of the process according to the present invention theFischer-Tropsch product stream of step (a) is separated to obtain atleast a fraction comprising 10 to 17 carbon atoms and a fractioncomprising 18 to 300 carbon atoms.

The separation is preferably performed by means of a distillation atatmospheric or slightly below atmospheric pressure conditions. It ispreferred that the distillation is carried out at a pressure of 500mbara to atmospheric and a temperature of 250 to 330° C. in the bottomsection of the column.

In step (c) of the process according to the present invention thefraction comprising 18 to 300 carbon atoms of step (b) is subjected to ahydrogenation step, thereby obtaining a hydrogenated fraction comprising18 to 300 carbon atoms. The hydrogenation is suitably carried out at atemperature between 200 and 275° C. and at a pressure between 20 and 70bar.

Typical hydrogenation conditions for hydrogenation of the abovefractions are described in e.g. WO2007/082589.

In step (d) of the process according to the present invention thehydrogenated fraction comprising 18 to 300 carbon atoms of step (c) isseparated to obtain one or more first light waxes having a congealingpoint in the range of 30 to 75° C. and a second heavy wax having acongealing point in the range of 75 to 120° C.

By light wax is meant wax having a congealing point in the range of from30 to 75° C. By heavy wax is meant wax having a congealing point in therange of from 75 to 120° C.

Suitably, the hydrogenated fraction comprising 18 to 300 carbon atoms ofstep (c) is separated by vacuum distillation at a pressure between 5 and20 mbar, preferably between 5 and 15 mbar, and more preferably between10 and 15 mbar. Also the distillation is preferably carried out at atemperature of from 300 to 350° C.

Preferably, the first light one or more waxes are obtained as distillateand/or side cuts in vacuum distillation, e.g. a first light wax fractionhaving a congealing point in the range of from 30 to 35° C., a secondlight wax fraction having a congealing point in the range of from 50 to60° C., and a third light wax fraction having a congealing point in therange of from 65 to 75° C.

Suitably, the first light wax fraction is obtained as top cut of thevacuum distillation, the second light wax fraction is obtained as a sidecut of the vacuum distillation and the third light wax fraction isobtained as heavier side cut of the vacuum distillation.

Preferably, one or more light wax fractions having a congealing point inthe range of from 30 to 75° C. of step (d) are hydrofinished therebyobtaining one or more hydrofinished wax fractions having a congealingpoint in the range of from 30 to 75° C. Suitably, a wax fraction havinga congealing point in the range 30 to 75° C. is hydrofinished therebyobtaining a hydrofinished wax fraction having a congealing point in therange of from 30 to 75° C.

Optionally, the first and second light wax fractions are hydrofinishedthereby obtaining a first light hydrofinished wax fraction having acongealing point in the range of from 30 to 35° C., and a second lighthydrofinished wax fraction having a congealing point in the range offrom 50 to 60° C.

Preferably at least the third light wax i.e. the heaviest side cut ofthe vacuum distillation step is hydrofinished thereby obtaining ahydrofinished wax fraction having a congealing point in the range of65-75° C.

Typical hydrofinishing conditions for hydrofinishing of the abovefractions are described in e.g. WO2007/082589.

In step (e) of the process according to the present invention, the heavywax of step (d) is separated thereby obtaining distillate wax having acongealing point of at least 75° C., preferably of at least 80° C.

Preferably, the second heavy wax of step (d) is separated, therebyobtaining at least one distillate wax fraction having a congealing pointin the range of from 75 to 85° C. and at least one residual wax fractionhaving a congealing point from 95 to 120° C.

Further, the heavy second wax of step (d) is separated, therebyobtaining at least one distillate wax fraction having a congealing pointin the range of from 70 to 90° C., preferably 70 to 85° C. and morepreferably 75 to 85° C.

In step (f) of the process according to the present invention, thedistillate fraction of step (e) is hydrofinished thereby obtaining ahydrofinished distillate wax having a congealing point of at least 75°C., more preferably of at least 80° C.

Suitably, the heavy distillate wax fraction having a congealing point inthe range of from 75 to 85° C. is hydrofinished thereby obtaining ahydrofinished heavy distillate wax fraction having a congealing point inthe range of from 75 to 85° C.

Further, the heavy distillate wax fraction having a congealing point inthe range of from 70 to 90° C., preferably in the range of from 70 to85° C. and more preferably in the range of from 75 to 85° C. arehydrofinished thereby obtaining hydrofinished heavy distillate waxfraction having a congealing point in the range of from 70 to 90° C.,preferably in the range of from 70 to 85° C. and more preferably in therange of from 75 to 85° C.

Preferably, the heavy residual wax fraction having a congealing point inthe range of from 95 to 120° C. is hydrofinished thereby obtaining ahydrofinished heavy residual wax fraction having a congealing point inthe range of from 95 to 120° C.

Typical hydrofinishing conditions for hydrofinishing of the abovefractions are described in e.g. WO2007/082589.

The heavy second wax of step (e) is preferably separated by short pathdistillation at a pressure between 0.05 and 0.5 mbar, and morepreferably between 0.1 and 0.3 mbar. The distillation is preferablycarried out at a temperature of from 200 to 350° C. and more preferablyfrom 250 to 300° C.

Typically, the distillate wax fraction having a congealing point of atleast 75° C., preferably of at least 80° C. is obtained as thedistillate fraction of the short path distillation. By the termdistillate is meant a fraction obtained with distillation which is a topcut or side cut but not a residual bottom fraction.

Short path distillation, also known as molecular distillation is knownin the art and therefore not described here in detail. An example of aform of short path distillation is a Wiped Film Evaporator. Typicalshort path distillations are for example described in Chapter 9.1 in“Distillation, operations and applications”, Andrzej Górak and HartmutSchoenmakers, Elsevier Inc, Oxford, 2014.

FIG. 1 schematically shows a process scheme of the process scheme of apreferred embodiment of the process according to the present invention.

For the purpose of this description, a single reference number will beassigned to a line as well as a stream carried in that line.

The process scheme is generally referred to with reference numeral 1.

In a Fischer-Tropsch process reactor a Fischer-Tropsch product stream isobtained (not shown). This product is separated in a distillation column2 into a fraction 10 comprising 10 to 17 carbon atoms and a fraction 20comprising 18 to 300 carbon atoms. Fraction 20 is fed to a hydrogenationreactor 3 wherein fraction 20 is converted to a hydrogenated fraction30. Fraction 30 is distilled in a vacuum distillation column 4 torecover one or more wax fractions 40 having a congealing point in therange of from 30 to 75° C. and a heavy fraction 50. Fractions 40 is fedto a hydrofinishing reactor 5 wherein fractions 40 is converted tohydrofinished fractions 60 having a congealing point in the range offrom 30 to 75° C.

Heavy wax 50 is distilled in a short path distillation column 6 torecover a distillate wax fraction 70 having a congealing point of atleast 80° C.

Fraction 70 is fed to a hydrofinishing reactor 7 wherein fraction 70 isconverted to a hydrofinished fraction 80 having a congealing point of atleast 80° C.

The fraction 10 is fed to a hydrogenation reactor 8 wherein fraction 10is converted to a hydrogenated fraction 90 comprising 10 to 17 carbonatoms.

The present invention is described below with reference to the followingExamples, which are not intended to limit the scope of the presentinvention in any way.

EXAMPLES Example Preparation of Fischer-Tropsch Derived Paraffin WaxFractions Having a Congealing Point of at Least 80° C.

A Fischer-Tropsch derived paraffin wax having a congealing point of atleast 80° C. was obtained using a Fischer-Tropsch process. To this end aFischer-Tropsch effluent was prepared according to the method describedin U.S. Pat. No. 6,858,127. Based on C1+ hydrocarbons the effluent had aC30+ content of 51.1% m and a C60+ content of 28.5% m.

The effluent was separated in a fraction A which is in the gas phase atambient conditions and a fraction B which is in the liquid or solidphase at ambient conditions. For all distillations described below carewas taken to avoid temperatures above 370° C. for any part of thedistillation equipment in contact with hydrocarbons and to avoid contactof hydrocarbons with oxygen. All distillations described below werecarried out in a continuous mode.

Fraction B was subjected to a distillation at atmospheric pressureyielding a top stream comprising a fraction containing molecules with 9or less carbon atoms, a side cut C containing molecules with 10 to 17carbons atoms and a bottom stream D containing molecules with 18 to 300carbon atoms. The effective cutpoint for the separation between streamsC and D was 310° C.

Fraction C was hydrogenated over a nickel catalyst as described in WO2007/082589 (Catalyst G). Process conditions were: a weight hourly spacevelocity (WHSV) of 1.0 kg/l/h, 30 bar of pure hydrogen at reactor inlet,a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 220°C.

The hydrogenated product was separated in a fraction E which is in thegas phase at ambient conditions and a fraction F which is in the liquidphase at ambient conditions. Fraction F consists of hydrogenated normalparaffins in the C10 to C17 range.

The residue of the atmospheric distillation (fraction D) was subjectedhydrogenated over a nickel catalyst as described in WO 2007/082589(Catalyst G). Process conditions were: a weight hourly space velocity(WHSV) of 1.0 kg/l/h, 30 bar of pure hydrogen at reactor inlet, ahydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 220° C.

The hydrogenated product was separated in a fraction G which is in thegas phase at ambient conditions and a fraction H which is in the solidphase at ambient conditions. Fraction H consists of hydrogenated normalparaffins in the C18 to C300 range.

Fraction H is subjected to a vacuum distillation. The distillation wasrun at a bottom temperature of 320° C. and a pressure of 15 mbar. Theeffective cutpoint between bottom stream and heaviest distillate was490° C. Several refined waxes were obtained as distillates of which theheaviest was subjected to a hydrofinishing operation over a nickelcatalyst as described in WO 2007/082589 (Catalyst G). Process conditionswere: a weight hourly space velocity (WHSV) of 1.0 kg/l/h, 60 bar ofpure hydrogen at reactor inlet, a hydrogen over feedstock ratio of 1000Nl/kg and a temperature of 240° C.

The residue of this vacuum distillation (fraction J) is subjected to ashort path distillation with an effective cut point of 540° C. Thedistillation was run at 0.2 mbar and 260° C.

The distillate of the short path distillation (fraction K) is subjectedto a hydrofinishing operation over a nickel catalyst as described in WO2007/082589 (Catalyst G). Process conditions were: a weight hourly spacevelocity (WHSV) of 1.0 kg/l/h, 60 bar of pure hydrogen at reactor inlet,a hydrogen over feedstock ratio of 1000 Nl/kg and a temperature of 240°C.

The product was separated in a fraction L which is in the gas phase atambient conditions and a fraction M which is in the solid phase atambient conditions. Fraction M is obtained as a refined wax with acongealing point of about 80° C. The yield of fraction M was 6.8% m ofthe Fischer-Tropsch effluent on a hydrocarbon basis.

Fraction M is the desired heavy Fischer-Tropsch based distillate hardwax. Properties of fraction M can be found in Table 1.

TABLE 1 Paraffin wax product (fraction L) Congealing point, ° C. 81.1 According to ASTM D938 Oil content, % w, 0.33 According to ASTM D721Saybolt colour^(a), cm 30+   According to ASTM D156 Cloud point, ° C.88    According to ASTM D5773 Kinematic viscosity at 3.95 120° C., mm2/sAccording to ASTM D445 ^(a)The Saybolt colour scale is used to quantifycolour intensity for mildly coloured substances in liquid state. Forthis objective waxes are molten for measurement. The scale runs from<−16 cm to >30 cm. >30 cm means water white. The higher the number thebetter (i.e. the lesser) the colour.

Discussion

The results in Table 1 show that starting from a hydrogenatedFischer-Tropsch effluent having C30+ content of 51.1% m and a C60+content of 28.5% m a Fischer-Tropsch derived paraffin wax having acongealing point of about 80° C. was obtained. Furthermore, the paraffinwax has a low oil content and a high Saybolt colour.

These observations indicate that the obtained refined Fischer-Tropschparaffin wax can be advantageously used in applications such as candles,hot melt adhesives, crayons, packaging, and PVC extrusion lubricants.

1. A paraffin wax having a congealing point according to ASTM D938 of atleast 75° C. and a Saybolt colour according to ASTM D156 of at least 25cm.
 2. A paraffin wax according to claim 1, having a congealing pointaccording to ASTM D938 in the range of from 75 to 85° C.
 3. A paraffinwax according to claim 1, having a congealing point according to ASTMD938 of at least 80° C.
 4. A paraffin wax according to claim 1, having aSaybolt colour according to ASTM D156 of at least 30 cm.
 5. A paraffinwax according to claim 1, having an oil content according to ASTM D721of less than 0.5 wt. %.
 6. A paraffin wax according to claim 1, whereinthe paraffin wax is a Fischer-Tropsch derived paraffin wax.
 7. A processto prepare a Fischer-Tropsch derived paraffin wax, the process at leastcomprising the following steps: (a) providing a Fischer-Tropsch productstream comprising paraffins having from 10 to 300 carbon atoms; (b)separating the Fischer-Tropsch product stream of step (a), therebyobtaining at least a fraction comprising 10 to 17 carbon atoms and afraction comprising 18 to 300 carbon atoms; (c) subjecting the fractioncomprising 18 to 300 carbon atoms of step (b) to a hydrogenation step,thereby obtaining a hydrogenated fraction comprising 18 to 300 carbonatoms; (d) separating the hydrogenated fraction comprising 18 to 300carbon atoms of step (c), thereby obtaining one or more first lightwaxes having a congealing point in the range of 30 to 75° C. and asecond heavy wax having a congealing point according to ASTM D938 in therange of 75 to 120° C.; (e) separating the heavy wax of step (d) toobtain a distillate wax fraction having a congealing point of at least75° C.; (f) hydrofinishing the distillate wax fraction of step (e)thereby obtaining a hydrofinished wax fraction having a congealing pointaccording to ASTM D938 of at least 75° C. and a Saybolt colour accordingto ASTM D156 of at least 25 cm.
 8. A process according to claim 7,wherein the heavy wax of step is separated in step (e) by short pathdistillation at a pressure between 0.05 mbar and 0.5 mbar.
 9. A processaccording to claim 7, wherein the heavy wax of step is separated in step(e) by short path distillation at a pressure between 0.1 and 0.3 mbar.10. A process according to claim 7, wherein the hydrofinished waxfraction has a congealing point according to ASTM D938 in the range offrom 75 to 85° C.
 11. A process according to claim 7, wherein thehydrofinished wax fraction has a congealing point according to ASTM D938of at least 80° C.
 12. A process according to claim 7, wherein thehydrofinished wax fraction has a Saybolt colour according to ASTM D156of at least 30 cm.
 13. A process according to claim 7, wherein thehydrofinished wax fraction has an oil content according to ASTM D721 ofless than 0.5 wt. %.
 14. A process according to claim 7, wherein thehydrofinished wax fraction has an oil content according to ASTM D721 ofless than 0.45 wt. %.
 15. A paraffin wax according to claim 1, having anoil content according to ASTM D721 of less than 0.45 wt. %.